1. Technical Field
The present invention relates to a power MOSFET device, and more particularly, to a power MOSFET device with a gate conductor surrounding source and drain pillar.
2. Description of Related Arts
Power MOS transistors are a specific type of MOS transistor used for providing and switching power in an integrated circuit. Accordingly, power MOS transistors must be able to work normally under high voltage. Therefore, it is typical for a power MOS transistor cell manufactured by a CMOS process to be of a larger size in order to is be capable of operations under high voltage. On the other hand, it is also a requirement for power MOS transistors to be able to output large currents. Therefore, it is also typical to combine a large number of power MOS transistor cells into a single power MOS transistor, wherein at least one power MOS transistor cell outputs a relatively small amount of current. However, such a power MOS transistor must be very large, which may be unacceptable in view of manufacturing requirements nowadays.
There are many published documents disclosing improved power MOSFET structure. For example, TW304302 discloses an improved planar power MOSFET structure with a sidewall spacer for reducing gate-source overlapping caused by lateral diffusion, U.S. Pat. No. 7,033,891 discloses a MOSFET device for RF applications that uses a trench gate in place of the lateral gate used in lateral MOSFET devices, and US 2008/0116510 discloses an improved trench MOS-gated device having a buried gate.